Hand tools for deburring sharp corners, using rotating blades, are known in the art. Such hand tools consist of a handle and a cutting blade, which is made of round wire that has been bent into the form of a crank. The blade rotates in a longitudinal hole of the handle, and the cutting edge of said blade follows along the edge of a hole or straight line of a part to be deburred. Such hand tools are used mostly in the metalworking and plastics industries.
FIG. 1 shows a known deburring tool 10. It consists of a handle 12 and a housing 14. Housing 14 may be made in a single piece with handle 12. Alternatively, handle 12 could be made as a separate part, which can be fastened removably to the housing. A blind hole 16 is drilled into the housing 14, into which the round shaft 18 of a cutting blade 20 is inserted. This round shaft 18 has a groove 22, into which a protrusion 24 enters, this protrusion being part of housing 14. Protrusion 24 prevents axial movement of the cutting blade 20, while still allowing free rotation of it in the housing. The cutting blade 20 has a cutting head 25 with a cutting edge 26. This cutting head 25 is bent, so the cutting edge 26 runs along a line, which lies outside the axis of rotation of shaft 18.
FIG. 2 shows an example of deburring the sharp edge of a hole 31 that was drilled into a workpiece 30. The blade 20 with its cutting edge 26 is inserted into hole 31 and, while being held by handle 12, a circular motion is performed, while exerting light pressure towards the workpiece. The blade 20 acts like a crank, so that its cutting edge 26 slides along the edge 32 of hole 31, and thereby removes the burrs that were created during the drilling operation. During this operation, the cutting edge 26 will automatically adjust itself to the correct cutting angle.
A similar hand tool is described in German patent application no. DE OS 2 129 768. This tool also includes a blade with a round shank which acts as a shaft, rotating in a tool holder which acts as a bearing. This tool holder is held in the handle. A disadvantage of these known deburring tools is the fact that their blades are difficult to manufacture. In addition, sometimes it is necessary to lock the rotatability of the blade. It would be difficult to apply a mechanism for blocking this rotation directly to the small round shaft of the blade, and such a mechanism would make a smooth rotation problematic.
Another hand tool for deburring holes and edges is described in French patent No. 2759930. This hand tool consists of a handle and a holding unit. There the holding unit is made of a shaft, which at its outer end is formed into a blade-holder. As shown there in FIG. 1 of French patent 2759930, the shaft 28 and the blade-holder 21 take the form of a crank. The shaft 28 rotates in bearing 25, and at its end 32 a counterweight 31 is fastened. The purpose of this counterweight is to ensure that whenever a user takes the tool into his hands, the holding unit will point upwards. The blade-holder has a longitudinal hole into which a cutting blade can be inserted. It also has a threaded cross-hole through which the cutting blade can be fastened.